Antifreeze composition



2,931,145 ANTIFREEZE- COMPOSITION Claude RossCutlip, Wilmington, DeL, and Richard David "Scheer, Kennett Square, -Pa., assig'nors to E. L du Pont 'derNemours and Compan -Wilmington, Del.,-a corpo- ,rati9n ,o- ,Delaware i 1 Drawin Application December. 2. 51955 g Serial ism-$54,621

4,C a .m (01. 252-75) This invention relates to antifreeze compositions suit- ,able for use as coolants in internal combustion engines and relates, more specifically to such compositions that become corrosive after extended use findtdmeans for preventing their inversionfrom the non-corrosive tov the corrosive state.

Theethylene glycol ,and similar ,polyhydric alcohol antifreeze solutions on the, market today meet practically United States ,Patcnt O 2,937,145 .Batented May .17, .1960

'2 corrgsiveto, a corxflsivestate. can, be avoided nts: and everyone of the -millions-of automotive cartnscr's. .Yet a anotherobjectis 'to .provide; an. ethylene glycol antifreeze -.whi chv is superioruto previously known antifreezesolu- 5 ;ti0ns. ,Otherobjectsland aduantagesof-rthe invention .will.hereinaftenappear. V

Research studies extending. over, a period of years have revealed thatglycol-typecorrosion inhibited antifreeze solutions, taken from cars after oneseasons use ,have ironcorrosion rates which are dependent-on the all the requirements of a permanent coolant for internal an. t ra elzi utstandinglyeffective sea-corrosion inhibitor .--;in alcoholic tantifreieze compo i ion ep e .11

I1 ,9 l1, l95). :Monyattempts vhavebeen madeto provide -;ir nproved;antifreeze s lutions, contai ng inhibito s;- other than sodium ::tetraborate. .Despite theseanumerous att-tempts, ,much ;ofthe.;antif reeze manufactured in country at .theipresent timeqcontains the,sodium tetraborate :corrosion, inhibitor disclosed by Kepfer.

It has-been discoveredin--recent,years, however, that an: improved corrosion inhibiting-action can-be obtained by using paired inhibitors, e.g. by pairing sodium tetra- -borate 1 with- -mercaptoben zothiazole (Keller, 2,373,570)

on by;- employ ing= an alkali metal; tetraborate in combinaanon withuan lkali-metalphosp at (Dun '.U.S. application S.N. 337,207, filed May 25, 1940, now n n d;

amount of reserve alkalinity asshown below: 7

Iron Corrosion Solutions Taken From Cars Rate/Thouandths of an 5 Inch Per Year None of the reserve alkalinity lost (basic solution) I 9 Half of the reserve alkalinity lost (basic solution) 30 Threequarters of the reserve alkalinity lost 100 allot the reserve alkalinity lost (acidic solution) 600 :These studies; andothers support the conclusion that a solution that has lOStzllO; morethanhalf of itsfreserve alkalinity may safelybe used for a second winter season,

'..while.those-witha greaterloss should be drained-to avoid 5 undue corrosion.

While-these-results can-be-arrived at by. carefully. con- -trolledstudies of car operation supported .by laboratory analysis of!antifreeze-solutions, facilities for analyzing spent or partially spent antifreeze solutions are not avail able-to the car'user orto the unskilled garage mechanic .who have the primary responsiblity-to'examine the radiator solutions of the many-millionsof cars on the-roads today. Consequently, such solutions haves-been and are ordinarily discarded, willynilly, in the interest of safety,

-aftera single year's use. 7

The inventionis dirccted'to the prepar'ationof glycol- -typeantifreeze solutions that the ordinary user'of an automobile, the-mechanic, and others unskilled in'reshouldbe retained or replaced. The problem of developdiscovery of;the ;-syne1 gi stic-. actionwof theasodium tetra- 1 ,borate-mercaptobenzothiazole inhibitor has made possible the manufacture of antifreeze compositions which remainmoncorrosive forrnore extensive; periods oftime.

';The pairing of an alkali metal tetnaborate with an a lkali metal phosphate alsohas-given-rise to anti-freeze compositions superior to thoseobtainable-by the use of individual inhibitors.

The above described corrosion inhibited glycol-type undiluted composition of the invention contains from solution in which the inversion from an initial non- 60 antifreeze solutions, while virtually unsurpassed from the --search and in-chemistry, can examine anddetermine, to --his own satisfaction, whether or not the usedhntifreeze ,ing sucha solution was a diflicult one. The'problem -lras-been-before the industry for a number of years-with no satisfactory answer, for obviously the general public 5 neither has available for use the facilities of a research laboratory nor training to use such'facilities, were-they -available. ,The solution totheproblem must provide some extremely simple means'of-recognizing the inversion of the antifreeze solution. i

,3 .Theantifreeze glycol-type solution .of the invention jpotentiallyprovides the means and withit the solution to ,theproblem. ,This antifreeze is initially provided in con centratedform with an alkali metal meta borate corrosion inh ibitor.and. a stable 'dyethat changes color when'the 5 solution invertslfrom the non-corrosive to the corrosive state. With such;a solution injhis car radiator, the ordinary car owner for the first time is able, by simple observation of the color of the solution, to determine its utility and whether or not it should be discarded.

ployedin the practice of the invention-contain watersoluble polyhydric alcohols, e.g., ethyleneglycol, propylene glycols, bu'tylene glycols, glycerol, etc., or mixtures thereof, as freezing point depressants. The preferred to 96% by weight of the polyhydric alcohol or alcohols.

The quantity of alkali metal meta borate employed as corrosion inhibitor should be 0.5 to 7.5% of the weight of the alcohol. The alkali metal meta borate may be added to the ethylene glycol directly or formed in situ by adding an alkali metal boratc together with an alkali The alcoholic antifreeze compositions which are em- 3 7 metal hydroxide to the solution. Organic inhibitors, such as mercaptobenzothiazole compounds (e.g. mercaptobenzothiazole, alkali metal mercaptobenzothiazoles, etc.), di-isoproply amine nitrite, mono.-, diand tri-ethanol amine and salts thereof, etc. may be used in combination -withthe alkali metal meta borate inhibitor, if desired.

The weight of organic inhibitor, when one is used, should be from 0.0001 to 0.5%, based on the weight of alcohol. These organic inhibitors may be omitted altogether, if desired, or they may be used in extremely small quantities.

The dyes used in the antifreeze solution are limited to those that (1) have one distinctive color in the noncorrosive solution and another distinctive color in the corrosive solution; (2) have the color change in the proper pH range to give optimum protection, i.e. between about 7.5 and 6.5; and (3) are not decomposed during normal use by the drastic changes of temperature and other conditions extant in the car radiator. The dye found to satisfy these rigorous requirements is phenolsulfonephthalein and it is used to the extent of from 0.01 to 0.5 gram/liter of the antifreeze solution.

In the examples of the anti-corrosion antifreeze solutions of the invention given below, the percent is by weight unless otherwise stated.

Example I.An anti-corrosive antifreeze solution is prepared having this composition:

As prepared, the solution has a pH of about 7.5 and has a red color. The solution when diluted to 50% with water, the concentration usually employed in an automobile radiator to give the desired cold weather protection, has a pH of about 9.0 and a somewhat deeper .red coloration. A solution containing the listed ingredients was used as an anti-corrosion antifreeze in a number of automobile radiators and retained the initial red color for more than 65,000 testmiles. In those radiators in which corrosion developeddue to excessive oxidation or other causes, and the pH, dropped below about 6.8, the solution had less than three-quarters of its reserve alkalinity and the color changed from the initial deep red to a distinct yellow.

Example II.-An anti-corrosive antifreeze solution is prepared having this composition:

Ethylene glycol percent-.. 95.00 Sodium meta borate do 2.75 Water ...do 2.25 Phenolsulfon'ephthalein g./liter 0.15

This anti-corrosion antifreeze'solution, as described, and when diluted with water for use in an automobile cool- .ing system has a distinctive red color which changes to I ,4 v Example III.-An anti-corrosive antifreeze solution is prepared having this composition:

This antifreeze solution has ample reserve alkalinity to protect automobile cooling systems from corrosion and, if through oxidation or other cause, develops acidity, such that reserve falls below an amount that reduces the pH of the solution below about 6.8, the color of the solution will change from a red to a yellow.

The term antifreeze solution" as employed in the specification and claims includes the diluted antifreeze in the form in which it is circulated through the engine cooling jacket, and also the undiluted or partially diluted form which is suitable for packaging and shipping in accordance with the practice common in the trade.

' We claim: y

l. A colored anti-corrosive antifreeze solution that changes color during its inversion from a non-corrosive to a corrosive state, comprising--- Ethylene glycol percent 90.0-96.00 Sodium meta borate ..do.. 0.5-7 .5 Phenolsulfonephthalein g./liter.. 0.010.5 Water Remainder 0.1 inch per year during use and over a period in which the reserve alkalinity changes from full reserve alkalinity to one-quarter reserve alkalinity, the solution of ingredients comprising a .polyhydric alcohol of the group consisting of glycols and glycerol as the major ingredient and as a minor ingredient, phenolsulfonephthalein, present in sufficient amounts to change the color of the antifreeze solution when the reserve alkalinity falls to-onequarter of the original reserve alkalinity'and to a rate of corrosion greater than 0.1 inch per year. I

3. The antifreeze solution of claim 2 in which the phenolsulfonephthalein changes the color of the solution as the reserve alkalinity decreases and the pH falls from 8.5 to 6.5. a

4. The antifreeze solution of claim 3 in whichthe polyhydric alcohol is ethylene glycol and the reserve alkalinity is obtained from 0.1 to 7.5% by weight of sodium met borate.

References Cited in the file of this patent UNITED STATES PATENTS 1,915,965 Williams June 27, 1933 2,054,282.- Clarkson et al Sept.'15, 1936 2,225,866 Holtzclau et a1. Dec. 24, 1940 2,249,867 Snelling July 22, 1941 2,373,570 Keller Apr. 10, 1945 

1. A COLORED ANTI-CORROSIVE ANTIFREEZE SOLUTION THAT CHANGES COLOR DURING ITS INVERSION FROM A NON-CORROSIVE TO A CORROSIVE STATE, COMPRISING- 